During the last 20 years, analogue, high frequency repeaters in data communication systems have been neglected in favour of digital concepts. Analogue gain may be realised with analogue or digital signal processing methods and are characterised firstly by their full or part transparency. They offer an amplified, analogue representation of the input signal to give a near sustained bandwidth and very low latency even at very large system bandwidths. Digital repeaters are not transparent and are commonly based on just one type of modulation as well as one type of communication protocol, which again is likely to be of proprietary character. The resulting conversion that takes place within them causes high supply current draws and they tend to be of large physical dimensions. In addition each repeater contributes to a substantial reduction of the overall bandwidth of the system and always introduces problematic latencies that either excludes or complicates certain modern, time critical telecommunication services. There are physical limitations as well to which extent technologies within digital repeaters can be developed for large bandwidths. With known semiconductor types there are physical limits to how much it is possible to reduce current consumption at high processing speeds being limited, amongst other factors, by the lower limit of transistor bias and clock frequencies. Such concepts are likewise not inexpensive in production as for instance due to their obligation to utilise the newest and most expensive technology available. Such technologies are therefore likely to be quickly replaced by new generations leading to hi write-off costs. As a consequence, it is too expensive and impracticable to use a sufficient number of such repeaters for, as an example sustaining signal levels on cables or for wireless coverage in an area where line of sight obstructions are significant. There exists therefore a great need of novel solutions that will give repeaters that may be utilised in great numbers and have low productions costs, which have small dimensions and consume low currents. An analogue repeater system may as well be made compatible with any existing, none proprietary communication system and might be prepared for most future ones. Analogue repeaters do not have the disadvantages associated with mentioned digital repeaters. It has been claimed that analogue repeaters as opposed to digital repeaters accumulate noise. These are conclusions with substantial flaws in addition to the fact that digital repeater systems will accumulate noise that gradually reduces symbol bandwidth in addition to the band width reduction being caused by the latency associated with each repeater. It is known from analogue repeaters of old times used in telephone systems that they were able to convey the signals across the globe. With regenerative, super regenerative and super heterodyne analogue repeaters one may obtain regeneration of the signal which among other things is owing to averaging of noise similar to what happens when amplifiers are connected in parallel. The accumulated, systematic noise may be reduced with various measures. A significant number of analogue repeaters may be utilised without substantial degeneration of the signal if the repeater design measures are taken. The advantage of analogue repeaters is their significantly lower power consumption as compared to digital repeaters. This is particularly important when repeaters are battery powered or will have to live off currents flowing in conductors that the repeaters are coupled loosely to, for example by inductive means.
In repeater or transponder systems as given in patent documents NO20001057, NO20010132, NO20020112, PCT/NO01/00079, PCT/NO03/00004 it is shown how analogue repeaters and systems using analogue repeaters may be realised within none optimal cases for both wireless and wire bound concepts or a hybrid of those. Characteristic of such sub optimal cases as when conventional solutions are not applicable, is when sufficient attenuation between input signal and output signal easily does not lend itself to be made larger than the signal gain of the repeater. Consequently it is also characteristic of such cases that there are points along the signal medium where analogue gain is required but where it is impractical to insert the mentioned attenuation. Examples of this are cable connections that cannot be broken up as in power grid networks. One example of wireless applications is when only one antenna can be used or when large distance in the form of a number of wavelengths between antennas cannot be realised. Additional examples of none optimal cases are when isolation between input and output signal is reduced from reflections from various causes. This may be the case for wire bound and wireless systems. In wire bound systems certain control of this may usually be exercised in wireless systems varying reflection parameters are often a larger problem. A one port gain block that is a repeater is stabile only as long as sufficient attenuation is present between the gain block or repeater and the reflection occurring in the system or repeater cascade. There exists therefore a need for novel, simple solutions making it more practicable to meet such challenges. In some cases conventional concepts have applied circulators to attain attenuation of reflections and to obtain directional sensitivity. However, in large scale context this is too expensive and additionally it is often impracticable. Even other types of directional sensitivity may be impracticable to implement. The consequences of insufficient attenuation between input and output signal in signal repetition using frequency transposing is duplex interference.
The consequences under the mentioned, none optimal conditions as a result of reflections or lack of attenuation may be that stability requirements cannot be sustained for signal repetition within the same channel.
When frequency transposing is applied to analogue repeater systems it is often important that a minimum of channels are used for duplex purposes in order to acquire the largest possible efficient symbol bandwidth using the available frequency spectrum in addition to securing channels for two-way communication or multiple channel systems for increasing the available system bandwidth. In this context it is also necessary to be able to allocate neighbouring channels as close to each other as possible. Super regenerative frequency mixers allow very small spacing between input and output channel in a repeater as shown in the publications NO20001057, NO20010132, NO20020112, PCT/NO01/00079, PCT/NO03/00004. There exists a need for novel applications that can economise the use of available, useful channels in such systems. This is particularly important for modern broadband applications. It is also particularly important in wireless applications where frequency band density is heavy. Even more important may this be in cable based systems, especially cables with poor high frequency characteristics where often just marginal frequency regions are available for the symbol bandwidth required now and in the future.
When gain is larger than 1 within the same frequency region for a repeater the stability criteria are important for utilisation of the gain. Reflections and echo from other repeaters play an important role to achieve stability. Phase is affected by the complex impedance that the gain block (amplifier) looks at and by the attenuation between ports of a multiple port gain block Analogue gain has to a large extent been abandoned in modern networks due to the difficult task of combining stability and satisfactory gains. It is especially difficult to make solutions that are both repeatable and possibly producible in large quantities or large systems. Directional attenuation in some form is often the only and the best measure taken against echo and reflections. In some applications attenuation of interference of 10 to 20 dB is satisfactory, but in other applications that require good linearity as with QAM and OFDM attenuation of 30-50 dB is necessary. For some modulation types problems with frequency beating can occur even with relatively large attenuation. Previously published solutions are not able to satisfy attenuation requirements and these solutions are either not practically applicable or have only limited applications as for example in none linear systems, for example frequency modulation for rather limited bandwidths. Therefore it exists a large need for novel, practical solutions that can give repeatable stability combined with required gain and signal to noise ratio. There is a need for such solutions both for signal repetition with frequency transposing and with same channel amplification.